Geotechnical talks

This post is devoted to Karl Terzaghi. Karl Terzaghi who is known as father of geotechnical engineering is among my favorites. His concepts of soil and its behavior had given this world entirely new outlook towards soil mechanics. I would like to post brief history of Karl Terzaghi.

Biography of Karl Terzaghi:
Karl Terzaghi was born in Prague on 2nd October1883. In 1904, he graduated from the Technische Hochschule in Graz, Austria, with an undergraduate degree in mechanical engineering. After his graduation he served one year in the Austrian army. Following his army service, Terzaghi studied one more year, concentrating on geological subjects. In 1908, his first job was as a junior design engineer for the firm Adol Baron Pittle, Vienna. And Karl became involved in the geological problems the firm faced. He went on with great success to an even more chaotic project in St. Petersburg. During the six months in Russia, he developed some novel graphical methods for the design of industrial tanks, which he submitted as a thesis for his doctorate at the University. In January 1912, he received the degree of Doctor of Technical Sciences from his alma mater in Graz. In America, on his own, he undertook an engineering tour of major dam construction sites in the West. This was no ordinary tour, but was his opportunity to gather reports and first-hand knowledge of the problems of many different projects, and he used it to the fullest before returning to Austria in December 1913. When war broke out, he found himself drafted into the army as an officer directing a 250 man engineering battalion. His responsibilities again increased, leading now 1000 men, and he faced combat in Serbia and witnessed the fall of Belgrade. After a short stint managing an airfield, in 1916 he became a professor in the Imperial School of Engineers in Istanbul. He set up a laboratory using only the most rudimentary of equipment, and began his revolution. His measurements and analysis of the force on retaining walls were first published in English in 1919, and was quickly recognized as an important new contribution to the scientific understanding of the fundamental behavior of soils. After the end of World War I, he accepted a lectureship at the American Robert College in Istanbul (1918–1925). There he began his research work on the behavior of soils and settlement of clays and on the failure due to piping in sand under dams. In 1924 he published much of this in his Magnum Opus, Erdbaumechanik which revolutionized the field to great acclaim. It resulted in a job offer from the Massachusetts Institute of Technology(MIT), which he immediately accepted. 1925-1929 he had done Lectureship at Massachusetts Institute of Technology. One of his first tasks in the USA was to bring his work to the attention of engineers. This he proceeded to do by writing a series of articles for the Engineering News Record, which were published in the winter of 1925, then as a small book in 1926. In 1928 he met the young Harvard doctoral student in geology, Ruth Dogget, and fell deeply in love. In 1929 he accepted a chair at the Vienna Technische Hochshule. He married Ruth, who became his editor and collaborator as well. In 1938 Terzaghi emigrated to the United States and took up a post at Harvard University. Before the end of the war, he consulted on the Chicago Subway system, the New Port News Shipways construction, and raising the Normandie, among others. He became an American citizen in March 1943. He remained as a part-timer at Harvard university until his retirement in 1953 at the mandatory age of 70. In July of the next year, he became the chairman of the Consulting Board for the construction of the Aswan High Dam. He resigned this post in 1959 after coming into conflict with the Russian engineers in charge of the project, but continued to consult on various hydroelectric projects, especially in British Columbia. The American Society Of Civil Engineers established in 1960 the Karl Terzaghi Award to an "author of outstanding contributions to knowledge in the fields of soil mechanics, subsurface and earthwork engineering, and subsurface and earthwork constructionMap of Egypt showing the location of Aswan and Lake Nasser. On October 25, 1963 he died in Winchester, Massachusetts

Books:

Terzaghi, K., "Large Retaining Wall Tests", Engineering News Record Feb.1, March 8, April 19 (1934).
Terzaghi, K., Theoretical Soil Mechanics, John Wiley and Sons, New York (1943).

Terzaghi, K., Proctor, R. V. and White, T. L., "Rock Tunneling with Steel Supports," Commercial Shearing and Stamping Co. (1946).

Terzaghi, K., From theory to practice in soil mechanics;: Selections from the writings of Karl Terzaghi, with bibliography and contributions on his life and achievents John Wiley and Sons (1967).

Terzaghi, K., American Society of Civil Engineers, "Terzaghi Lectures, 1974-1982," American Society of Civil Engineers (1986).
Terzaghi, K., Peck, R. B. and Mesri, G., Soil Mechanics in Engineering Practice, 3rd Ed. Wiley-Interscience (1996).

References:
R. E. Goodman, Karl Terzaghi, American Society of Civil Engineers, 1999.

Among my various other stone column projects one of the interesting project was installation in order to reduce the Soil liquefaction potential. We were working in the region which was prone to earthquake and comes in zone IV. We need to do stone column of various depths and lots of free boring. It means that we had to leave free bore for certain depth below ground level and below that we had to install actual stone column. This whole assignment was done with wet method.

Project Description:
Indian railways (Our Client) had identified two zones in the plant area which is susceptible to high liquefaction potential. First zone is at the main plant building and second location was at time office. At main plant area cast wheel manufacturing unit was about to set up. In order to mitigate high liquefaction potential at these two regions stone columns are to be installed. Stone column installation substantially increases the density of the soil and simultaneously increases the rate of excess pore water pressure dissipation. Finally stone column helps in increasing the stiffness of the soil which was earlier susceptible to high liquefaction potential.

Technical specification:
Vibro stone column of 750 mm dia is to be installed at 2.8m square spacing c/c. Top 6.7 m from the existing ground level is free boring and below this actual installation work is to be done up to the depth of 12m. Area replacement ratio was 5.6%.Above stone column 300 mm course sand will be laid and above that PCC will be done to start foundation work.

Soil liquefaction is the phenomenon when due to sudden load soil changes its solid state into liquefied state. When saturated soil (sand and silt) is subjected to earthquake its strength and stiffness is reduced. In saturated soil space between individual particles is completely filled up with water. When saturated soil is subjected to earthquake excess pore water pressure develops because of which soil particles readily moves and simultaneously it behaves like liquid and looses its stiffness. Due to this phenomenon soil looses its ability to support structures, can even lead to very gentle slope failure and even lead to soil boiling.

Mechanism which cause soil liquefaction:

Strain softening soil: Soil like loose sand is susceptible to liquefaction when either static or cyclic load is applied on it and it’s greater than its ultimate stress. In this type of situation flow liquefaction occurs.

Strain softening soil: Dense or moderately dense soil is susceptible to cyclic softening when cyclic undrained load is applied on it. This type of phenomenon leads to cyclic liquefaction.

Vibro Replacement methods of construction of stone column through weak soil and filled up soil is basically used in order to increase the load bearing capacity of soil and reduce settlement characteristics. It provides an economical and technically sound solution of geotechnical and foundation problems. Other than taking care of bearing capacity of the soil, stone column is also sometimes used in order to reduce the Soil liquefaction potential of the soil.

For stone column construction vibrator is allowed to penetrate to the designed depth using its self weight with water pressure (Wet Method) or air pressure (dry method). Resulting cavity is filled up with stone which will be free of clay and silt fines. The filled up stones and surrounding soils is properly interacted and compacted in stages.

The stone column spacing and basic design is based on load applied, soil type and requirement of settlement. In general spacing of stone column varies from 1.2 to 3 meters.

The two methods of constructing Vibro replacement stone columns:
Wet method: In this method boring is done using water pressure and simultaneously compaction is carried on.
Dry method: In this method boring is done using air pressure.

In late 1600 BC and 1100 BC Geotechnical engineering was known with different names. Various archeological findings and literature resources of ancient Greece civilization of Mycenaeans time had established that geotechnical engineering had flourished during that time. Various archeological remains justify there construction practices of the monuments. The literatures of Mycenaeans civilization in the form of plates and various other written texts in the form of poems had provided large amount of geotechnical practices applied there.

According to the findings Various Geotechnical projects which was undertaken during there time are as following.

i) Fortifications

ii) Underground shafts (graves)

iii) Retaining walls

IV) Roads/Pavements

v) Bridges

vi) Hydraulic works

vii) Dams/Embankments

viii) Tunnels

ix) Harbors

x) Quarries/Mines

xi) Residential construction

With the evolution of civilization, engineering and art also developed. It’s said that civil engineering came into existence when human being developed art of living. Among all the other engineering Civil engineering is known as the mother. It has given birth to all other engineering sciences. Among the various other specialized engineering science of civil engineering Geotechnical Engineering plays very important role.

It’s said that Geotechnical Engineering came into existence long back some where in 17th century. During that time piling work was done with the help of pile boring machine which looks like this.